Modern high performance gas turbines have intake temperature proximate 2,000K. In order to protect the blades, forming a cooling gas film on the metal surface of the blades through cooling airflow generated by free jet is one of the most commonly used methods to reduce the thermal stress load of the gas turbine blades.
According to liquid state stability theory, a jet has an unstable state with a symmetrical eddy, which is generated by mixing natural jet with external air. As the shearing stress generated by velocity causes turbulence to grow exponentially toward downstream, after the most unstable fluctuation has grown to a certain degree, a nonlinear effect is generated and an eddy with a regular arrangement and specific frequency by rolling up is formed as shown in FIG. 1. As a result, a certain distance after ejection, the free jet is mixed with high temperature airflow, and gas film can no longer be formed continuously to protect the metal surface.
Taiwan patent No. I257447 entitled “Micro tube cooling used on distal ends of turbine blades” discloses an embedded micro tube in a streamline body. It can eject cooling air from inside of the streamline body to an external area thereof, and the embedded micro tube has a plurality of ejection spouts, hence can effectively perform cooling for the streamline body. However, the embedded micro tube is complex in design and must be built inside the streamline body, it is quite difficult in fabrication.
Moreover, cooling is a problem not only happened to the turbine blades. In order to achieve desired cooling effect, conventional chips have to add radiation fins to increase cooling area, and a bigger air fan often is needed to disperse heat quickly. However, as the chip is shrunk constantly, the cooling method that adopts the radiation fins and air fan can no longer meet cooling requirement.